Brent,
Actually I wasn't being tongue in cheek, but perhaps more explanation is needed. Opportunity cost is a relative term and can be used in different contexts. Consider the following:
"Opportunity cost" of a resource, is the value of the next-highest-valued alternative use of that resource. If, for example, you spend time and money going to a movie, you cannot spend that time at home reading a book, and you can't spend the money on something else. If your next-best alternative to seeing the movie is reading the book, then the opportunity cost of seeing the movie is the money spent plus the pleasure you forgo by not reading the book.
So in the example from my previous post, while the financial cost is actually $100, the opportunity cost as it relates to the "value" of the next best thing is only $50. So its all relative to something else...but yes this doesn't show up on the books anywhere, just a benefical tool in doing cost-benefit analysis that can be applied in this thread.
If one will either travel to play golf, or stay at home and see a movie, then either way they will at least pay the cheaper amount to see the movie, so the true figure in determing the "cost" should be the delta between the two, even though the money leaving your wallet will still be the price of everything in the trip.